The present invention relates generally to transporting, unwinding and reforming a pipe and, more particularly, to an improved trailer for transporting a pipe coil, straightening and rerounding the pipe, and assisting in unwinding the pipe for laying in a trench.
Fluid natural resources are commonly supplied through underground piping. A particularly prevalent use of such pipe is in the natural gas industry. In recent decades, an industry-wide shift has been made away from the use of metal piping, which generally proved unreliable due to corrosion in the underground environment, and toward more reliable types of plastic piping. Initially, this pipe was formed of polyvinyl chloride (PVC) or the like. While the PVC pipe is corrosion resistant, other significant problems were presented by its use. First of all, the inherent rigidity of PVC pipe (also known as xe2x80x9cstick pipexe2x80x9d) dictates that it is available only in singular, elongate sections. Thus, to create a continuous underground pipeline, the on-site chemical or heat fusion of the ends of adjoining pipe sections is necessary. As should be appreciated, this operation is time consuming, labor intensive and requires specialized chemical or heat welding techniques and highly skilled workers to precisely complete the fusion.
To meet this need and overcome the aforementioned difficulties, there has been a recent shift away from the use of PVC pipe and toward the use of pipe made from other, more durable, flexible polymeric materials, such as, for example, polyethylene. One great advantage resulting from this advancement is the ability to store and deliver the pipe in coils comprised of several hundred, or even thousands, of feet of pipe. This of course makes substantially continuous pipe laying possible with only a few, infrequent interruptions to permit a worker to fuse the ends of adjoining coils together. Thus, as is now widely recognized throughout the industry, flexible polyethylene coil pipe results in a significant time savings over the prior art stick pipe laying operation, reduces the incidence of joint defects or failure due to the low number of fusion sites, and is also more durable in the underground environment.
Notwithstanding these vast improvements over the prior art metal and PVC piping, the use of flexible coil pipe is not without limitations. Perhaps the most significant limitation is the absence of an effective device for both transporting the coil to the work site and assisting in laying the pipe from the coil into a trench. Indeed, most minor repair jobs or branch lines require only one coil of pipe, or a portion of a coil, for completion. In these incidences, it is even more desirable to provide a device for efficiently transporting the coil from place to place, as well as to complete the pipe laying as necessary, without the need for support equipment.
Also, we have found that virtually all prior art transportation devices rely on a reel or spool to support the coil on the trailer or other vehicle. This arrangement is troublesome for several reasons. First of all, to avoid the additional expense associated with selling pipe pre-wound on such reels, the coil must be loaded onto the reel by the pipe laying contractor. As should be appreciated, this extra operation requires a significant amount of effort and time. The troublesome nature of the use of reels is compounded when it is considered that flexible pipe comes pre-coiled in a number of different diameters, depending on the size (cross-sectional diameter) of the pipe. Thus, in some prior art devices in order to accommodate the various diameters of coil, a number of different size reels must be made available by the manufacturer. Additionally, it has been our experience that reels tend to allow the coil to shift back and forth in an uncontrolled fashion, especially when the end of the pipe approaches. This increases the chance that the coil can become tangled or hung up on the reel and cause deleterious binding, which of course requires substantial downtime to correct.
And inherent problem characterizing the use of flexible plastic pipe is the tendency of the pipe itself to change shape when it is formed into the coil, especially after resting in a coiled position for an extended time. More particularly, the bending into the coil causes the pipe to assume a degree of curvature in the longitudinal direction, as well as an ovalness in cross-section. This deformation is sometimes referred to as xe2x80x9ccoil set.xe2x80x9d As can readily be appreciated, the curvature and ovalness makes the pipe difficult to control during unwinding. Such flexible pipe has a good memory and, thus, there is a tendency for the pipe to backlash to the original coiled position and maintain its oval shape during unwinding. Obviously, to make the pipe lay in the trench, it must be straightened, and to maintain the maximum cross sectional area it must be rerounded. If the pipe is not so properly and accurately reformed, this coil set would make it difficult to mate the ends of two adjoining coils of pipe for fusion. This is because the ends to be mated would tend to be at a slight angle to each other, and they would likely have slightly different degrees of roundness.
There have been attempts in the past to successfully combine straightening and rerounding of plastic pipe as it is being unwound from the reel or the like in analogous applications. For example, in U.S. Pat. No. 4,095,437 to Cox, an apparatus is provided having a plurality of opposed roller pairs alternatively mounted in upright and transverse positions to contact and straighten/reround pipe. Another example is shown in U.S. Pat. No. 4,527,639 to Dickinson, III, et al., which discloses a device for removing the curvature and ovalness from drill pipe that extends through a curved passage in a bore hole that changes directions.
A more recently proposed apparatus particularly tailored for use with flexible coils of polyethylene pipe is described in U.S. Pat. No. 5,676,009 to Bright et al. and assigned to Chevron. The xe2x80x2009 patent provides for a combined straightener and rerounder device that is towed behind a truck carrying a pipe coil. The device includes a set of straightener rollers to first remove the curvature, and then a set of side pressure rollers to remove the ovalness from the pipe. Although straightening and rerounding is achieved, other noteworthy limitations create problems. First of all, because the straightener/rerounder device remains in a fixed position behind the trailer, it can not track the pipe unwinding from the coil. This shortcoming can lead to the creation of deleterious pinch points and binding as the pipe is pulled from the periphery of the coil to the center fixed inlet of the device. In addition, loading of the pipe into the straightener requires a significant amount of time and effort. One or more workers must wrestle the end of the pipe and insert is over and under offset straightener rollers and then through separate rerounder rollers. It should also be recognized that the device does not itself carry the pipe coil and, thus this results in having to have a support a piece of equipment (truck or separate trailer) remain at the work site during the pipe laying operation.
Therefore, as should be appreciated from reviewing the foregoing description of the prior art, a need is identified for an improved trailer that both transports a coil of pipe to a work site and assists in laying the pipe from the coil into a trench. The trailer would eliminate the need for a reel or spool for supporting the coil, yet should provide proper support for the coil to ensure smooth rotation during the pipe laying operation. Adaptability for use with different diameters of coils would also be provided. In addition, the trailer would permit loading of the coil in an efficient and substantially effortless manner. To remove curvature and ovalness from the pipe unwinding from the coil, an improved on-board straightener/rerounder would also be provided that tracks the pipe during unwinding to more efficiently guide the pipe into the trench and reduce the tendency for binding during the pay-out. Overall, the trailer would significantly enhance the ease and efficiency of transporting and laying the pipe coil and at a significantly lower initial cost.
With the above needs in mind, it is a primary object of the present invention to provide an improved trailer that transports and assists in unwinding pipe from a coil for laying in a trench that overcomes the above-described limitations and disadvantages of the prior art.
Another object of the invention is to provide an improved coil pipe trailer with a cradle for contacting an outer surface of and supporting the coil, thereby avoiding the need for a separate reel or spool.
Still another object of the present invention is to provide an improved coil pipe trailer that includes at least one retainer for engaging an inner surface of the coil during the pipe laying operation, the retainer(s) being adjustable to accommodate a variety of sizes of coil.
A further object of the present invention is to provide a pipe trailer with a releasable gate for providing full access to the support cradle and the retainer(s), thereby permitting easy loading of the coil onto the trailer for transportation or unwinding.
Yet another object of the present invention is to provide a pipe trailer with an on-board straightener and rerounder for reforming the pipe to the curvature and ovalness from the pipe unwinding from the coil.
Still a further object of the present invention is to provide a pipe trailer wherein the straightener/rerounder is mounted for translational movement such that it tracks the pipe as unwinding occurs, thereby avoiding the creation of pinch points that tend to cause binding as the pipe is pulled from the periphery of the coil, and thus erratic pay-out of the pipe.
Additional objects, advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as described herein, an improved trailer for transporting coiled pipe and assisting in laying the pipe into a trench is provided. The hallmarks of the improved trailer are the improved support means that avoid the need for the reel to support the coil, as is characteristic of prior art trailers, and the provision of an on board reforming assembly having a unique straightener/rerounder that tracks the pipe unwinding from the coil to ensure smooth pipe pay-out. The pipe is also easily threaded through the reformer assembly to minimize the initial set-up time. In addition, provision is made for easy loading of coil on to the trailer through a swing out gate. Advantageously, this combination of features provides for the first time a significant increase in the ease and efficiency of the pipe transporting and laying operation, and does so at an overall lower initial cost.
More particularly in the preferred embodiment, support for the coil is provided by a cradle adjacent to a base forming the main body of the trailer. The cradle includes means for rotatably supporting the coil on its outer surface. Specifically, the cradle includes a pair of spaced support roller assemblies for contacting the outer surface of the coil as it freely sits in the trailer. A frame attached to said base supports a pair of upper retainer rollers for engaging the inner surface of the coil. To ensure that the support and retainer rollers can accommodate different sizes of coils, both are adjustable. More specifically, the support roller assemblies are pivotally mounted on the base to provide self-centering action for contacting the outer surface of any size standard coil. The retainer rollers are slidably mounted on the frame and held in place using manually operable locking pins. Together, these combined support and retainer rollers advantageously allow the coil to freely sit in the cradle and rotate during the pipe laying operation, thus avoiding the need for a troublesome reel or spool that is characteristic of prior art trailers. The automatic positioning of the self-centering roller assemblies and the manual release features of the retainer rollers also avoid the need for use of tools and/or other time consuming operations to complete the loading of the coil onto the trailer.
Also in the preferred embodiment disclosed, the unique straightener/rerounder of the pipe reforming assembly adds significantly to the efficiency of operation. As a first step in straightening, the pipe is forced downwardly as it leaves the coil against an initial horizontal bending roller. Adjacent vertical guide rollers keep the pipe centered in the concave face of the bending roller and direct the pipe further along the reforming assembly. The rerounder has a pair of opposed upstanding rollers for applying a combined vertical holding and horizontal compressive force to the pipe. This component provides the next step in straightening, as well as providing the full operation of removing ovalness. One of the upstanding rollers is selectively adjustable to vary the compressive force applied to the pipe. Downstream of these upstanding rollers in the preferred embodiment is a second horizontal bending roller leading into an adjustable pipe deflection assembly for final straightening. The deflection assembly includes an upper roller that is manually adjustable for contacting and varying the vertical deflection of the pipe relative to said second bending roller. Advantageously, these combined elements of the straightener create a backbend in the pipe that reverses the bending moment memorized by the pipe during its initial forming into a coil and during storage. In an alternative construction, the straightener includes a single horizontal bending roller that contacts the upper surface of the pipe as it transitions from the cradle to the rerounder reforming assembly, which avoids the need for the deflection assembly.
To facilitate loading of the pipe in the reforming assembly, the rerounder and deflection assembly are provided with easy release features. More particularly, the rerounder is provided with a releasable top gate which pivots upwardly to permit loading of the pipe coming from the first horizontal roller between the upstanding rollers. The pipe is then passed over the second horizontal roller and into the deflection assembly, which includes a fully releasable top portion that supports the upper roller.
In accordance with another important aspect of the invention, the pipe reforming assembly is carried on board the trailer. In the preferred embodiment, the reforming assembly is positioned so as to receive the pipe unwinding from the rear of the trailer. To avoid the creation of deleterious binding as the pipe is unwound, the reforming assembly is mounted such that it translates back and forth along the base. Thus, as the pipe moves across the coil during unwinding, the reforming assembly floats back and forth along the base tracking this motion. The concave face of the first horizontal bending roller and the pair of vertical guide rollers mounted adjacent the coil greatly assist in efficiently transferring the reciprocal motion of the uncoiling pipe to the reforming assembly. This feature results in a significant enhancement in the smoothness of the unwinding operation, and avoids deleterious binding and the associated downtime for correction.
Another important aspect of the present invention is the ease of both loading the coil into the trailer and feeding the pipe through the reforming assembly. Briefly describing the loading process, the frame includes a swing out gate that provides full access to the cradle and retainer rollers. The coil is lifted using a forklift, or other suitable means, and placed on the roller assemblies forming the cradle. These roller assemblies automatically pivot into place in response to the contact with the outer surface of the coil. The gate is then closed and the retainer rollers are moved into position and locked in place using the manually operable locking pins. The coil now freely sits in the trailer and is free to rotate to pay out the pipe.
To facilitate the placement of the pipe in the reforming assembly, the upper portion of the deflection assembly and the gate of the rerounder are released from the operative position. The free end of the pipe is pulled from the coil and placed over the initial horizontal bending roller and through the vertical guide rollers. Next, the pipe is passed through the open gate and between the opposed upstanding rollers of the rerounder. This leads the pipe to be positioned over the second horizontal bending roller, and onto the lower roller of the deflection assembly. The gate of the rerounder and the top portion of the deflection assembly with its upper roller are then both closed. Once the pipe is fully fed through the reforming assembly, the amount of compressive force applied by the rerounder and the amount of vertical deflection created between the second bending roller/deflection assembly are adjusted by the operator. With these few steps and relatively little effort, the pipe unwinding, reforming and laying operation is ready to begin. The key point is the avoidance of the troublesome, complicated reels of the prior art. The apparatus of the present invention advantageously allows for the entire loading operation to be completed in a matter of minutes and with minimum effort by the operator.
In addition to the support and retainer rollers, the trailer is also equipped with a plurality of bumper rollers for contacting the periphery of the coil during rotation. Preferably, the bumper rollers are mounted on the horizontal and vertical members of the frame in a direction perpendicular to the axis of rotation of the coil. These rollers serve the dual function of assisting the coil in smoothly rotating and lessening any frictional drag force that would otherwise result from contact between the sides of the coil and the frame members.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.